Technical Field
This invention relates to a semiconductor device and a method of manufacturing the same.
Related Art
A Schottky barrier diode (SBD) is a type of semiconductor device (semiconductor element) for which it is required to suppress leakage current at the reverse voltage by reducing the electric field crowding occurring at an end portion of a Schottky junction. To increase breakdown voltage, suppressing the leakage current at the reverse voltage by reducing the electric field crowding is important, particularly in semiconductor devices used as power devices.
JP08-139341A discloses a semiconductor device as a Schottky barrier diode including a Schottky electrode having a field plate structure formed on a semiconductor layer having a mesa structure. According to the technique of JP08-139341A, an insulating film formed on the mesa structure is partially removed from the upper surface of the mesa structure to form an opening in the insulating film. Then, the Schottky electrode is formed from the inside of the opening in the insulating film to extend along the periphery of the mesa structure. The semiconductor device of JP08-139341A can reduce the electric field crowding occurring at an end portion of a Schottky junction between the semiconductor layer and the Schottky electrode by using the mesa structure of the semiconductor layer and the field plate structure of the Schottky electrode.
The inventor(s) of the present invention have found that in the semiconductor device of JP08-139341A, as tightness of contact between the Schottky electrode and the insulating film reduces, so does the effect of reducing the electric field crowding from a side surface of the mesa structure. Thus, in the structure of JP08-139341A, the Schottky electrode is required to contact the insulating film tightly as well as to maintain a Schottky barrier height relative to the semiconductor layer. This causes a problem in that a material usable as the Schottky electrode must be selected from a narrow range of choices.
Further, in the semiconductor device of JP08-139341A, the Schottky electrode is formed on the semiconductor layer after the insulating film on the semiconductor layer is removed. In this regard, the inventor(s) of the present invention have also found that, even if tightness of contact between the Schottky electrode and the insulating film is ensured, reduction in the Schottky barrier height of the Schottky electrode is unavoidable depending on a material of the insulating film. This causes a problem in that in the structure of JP08-139341A, a material usable as the insulating film must be selected from a narrow range of choices.
Thus, it is desired a technique for a semiconductor device to sufficiently suppress the leakage current at the reverse voltage while allowing each of a material of a Schottky electrode and that of an insulating film to be selected from a wide range of choices. It is also desired a technique for a semiconductor device to achieve cost reduction, a higher level of fineness, ease of manufacture, resource saving, enhancement of usability, enhancement of durability, and the like.